Specific antigenic fractions of T. spiralis larvae that produce blastogenesis of spleen cells from infected mice will be used in attempts to sensitize normal mice against a challenging infection. Whole-body, X-irradiation will be used to test its effect on persistence of adult worms after a primary infection, and reconstitution will be employed in attempts to determine the cell type(s) involved in the expulsion mechanism. The localization and persistence of adult worms throughout the intestinal tract after a primary infection will be determined to obtain a better understanding of the pattern of expulsion of all worms. BIBLIOGRAPHIC REFERENCES: Larsh, J.E., Jr. 1975. The association in mice of intestinal inflammation, elevated levels of phospholipase B, and expulsion of Trichinella spiralis. Wiadomosci Parazytologiczne 21: 679-682. Larsh, J.E., Jr. and Race, G.J. 1975. Allergic inflammation as a hypothesis for the expulsion of worms from tissues: A review. Experimental Parasitology 37: 251-266.